As most will know, the USPS increased rates on most mail, but left the First Class "Forever" stamps at 44 cents. The most noticed change to the average consumer was that first class mail for each additional ounce was increased from 17 to 20 cents. In fact, the USPS spent millions of dollars (I would imagine) issuing new stamps in the 64 cent and 84 cent denominations (to replace the 61 cent and 78 cent issues that had formerly covered the second and third ounce first class mail rates).
Anyway, our household received some business mail the other day consisting of 6 letter size pages, which certainly required the second ounce postage, but in a meter situation, the USPS accepted the "old" rate, with no return to sender or postage due request to the recipient:

Granted that 3 cents is not worth fussing over, but I just wonder how many times this happens and whether or not the USPS gives a break to meter users when it comes to these sort of errors. Perhaps it's only a small amount in one instance, but if it is commonplace to see this happening in the thousands or millions of pieces of metered mail going into the postal system, errors like this can easily add up ... especially for a "cash-strapped" US Postal Service.